A focus state detection apparatus for detecting focus state on the basis of
signals outputted from a pair of area sensors each of which is configured
in two dimension in accordance with an image of an object passing through
an optical system and formed on the pair of area sensors. Each of the pair
of area sensors is divided into a plurality of areas each of which can be
controlled independently, and charging pixels of the area sensors is
controlled by each pair of corresponding divided areas of the area
sensors.